Field of the Invention
The present invention relates to a regulator for flow modulation to prevent the collapse of a blood vessel during blood collection and, more particularly, to a variable flow resistor that acts to slow down the initial flow rate of blood into an evacuated blood collection device. The present invention also minimizes the initial spike in flow rate caused by vacuum pressure and slows down the overall blood collection time to avoid rapid depletion of resident blood within the vessel.
Description of Related Art
Phlebotomy procedures are often carried out using a blood collection device or intravenous (IV) infusion device. A typical blood collection or (IV) infusion device includes a needle assembly having a cannula that includes a proximal end, a pointed distal end, and a lumen extending therebetween. The needle assembly also includes a hub with a proximal end, a distal end, and a passage extending between the ends. The proximal end of the cannula is mounted in the passage of the hub so that the lumen of the cannula communicates with the passage through the hub. A shield may be provided for shielding the distal end of the cannula after use. The blood collection set may also include a wing member that projects transversely from the hub or from the shield. The wings of the wing member can be folded with respect to each other to define a handle that facilitates manipulation of the needle assembly. The wings then can be rotated apart and held against the skin of the patient.
Typical blood collection devices may also include a length of flexible plastic tubing. The tubing has a distal end that is connected to the proximal end of the hub and communicates with the lumen of the needle cannula. The end of the plastic tube remote from the needle cannula may include a fixture for connecting the needle cannula to a blood collection tube or other receptacle. Phlebotomy procedures often employ evacuated tubes, such as the VACUTAINER® brand of evacuated tubes commercially available from Becton, Dickinson and Company. Evacuated tubes often are used with a tube holder that has a proximal end, a distal end, and a tubular side wall extending between the ends. The proximal end of the holder is generally open and configured for slidably receiving the evacuated tube. The distal end of the holder typically includes an end wall with a mounting aperture. The tube holder may be used with a non-patient needle assembly that has a non-patient hub configured for cooperation with the mounting aperture of the holder. The non-patient needle assembly further includes a non-patient cannula extending proximally from the hub and into the tube holder.
The blood collection set may be used by mounting the fitting at the proximal end of the flexible plastic tubing to the distal end of the hub of the non-patient needle assembly. The pointed distal end of the cannula is urged into a targeted blood vessel, such as a vein, by gripping of the wings of the wing member for manipulation of the cannula. The wings may then be folded into engagement with the skin of the patient and may be taped in position. An evacuated tube is urged into the open proximal end of the blood collection tube holder so that the proximal end of the non-patient needle pierces the stopper of the evacuated tube. As a result, the blood vessel of the patient is placed in communication with the interior of the evacuated tube, and the pressure differential between the blood vessel and the evacuated tube will generate a flow of blood through the cannula, the hub, the flexible tubing, the non-patient hub, the non-patient needle, and into the evacuated tube.
Collapse of the patient's blood vessel during blood collection can occur as a result of a pressure differential created by the connection of the evacuated tube to the non-patient needle cannula. This collapse can occur as a result of the blood being removed too quickly from the patient's blood vessel due to the vacuum draw of the evacuated tube. When a standard evacuated tube is connected to a blood collection set, there is an instantaneous introduction of a sharp vacuum pressure applied to the patient's blood vessel. This strong vacuum results in a spiked flow rate of blood out of the patient's blood vessel. This sharp outflow of blood can lead to the vessel wall collapsing against the bevel of the distal end of the patient cannula, resulting in flow stoppage.
Accordingly, a need exists for a vacuum pressure regulator which minimizes the incidence of vessel or vein collapse.